Question

hemophilia is a genetic blood disorder that is common in descendants of queen victoria. although several women in the family were carriers of the allele for the disorder, only men ended up actually expressing the disorder.
which statement is true about the inheritance of hemophilia?
it’s a dominant trait on the x chromosome
it’s a recessive trait on the y chromosome.
it’s a recessive trait on the x chromosome.
it’s a dominant trait on the y chromosome.

Explanation:

1. Recall X - linked inheritance: Hemophilia is an X - linked disorder. Males have one X and one Y chromosome, while females have two X chromosomes.
2. Analyze dominant/recessive and chromosome:

• Y - linked traits are passed from father to son, but hemophilia is not Y - linked (so options with Y - chromosome are wrong).
• If it were a dominant X - linked trait, heterozygous females (carriers) would express the disorder, but in the case of hemophilia, female carriers do not show the disorder, indicating it is recessive. So hemophilia is a recessive trait on the X chromosome.

Answer:

It's a recessive trait on the X chromosome.